To hide a hunter

Posted: Wednesday, December 10, 2008 7:35 PM by Alan Boyle

W.L. Gore & Associates This picture approximates a deer's-eye view of a bow hunter wearing Optifade camouflage. Click on the image to see how the scene would look to human eyes.

To hide yourself from the deer you're hunting, do you want to dress like a tree - or become invisible? Researchers are trying to take the second approach, with camouflage clothing that takes advantage of the fact that animals don't see the world the way humans do.

The Optifade camouflage pattern, created by W.L. Gore & Associates (the makers of Gore-Tex fabric), represents a break from the colored leaf patterns you see on stereotypical camo clothing. In fact, it looks a lot like the mostly monochromatic blocks-and-dots now used on military duds. That's no mistake: One of the advisers on the Optifade project was retired Lt. Col. Tim O'Neill, whom some regard as the father of modern-day military camouflage.

The design includes a big, blocky "macro pattern" that is meant to make the human form hard to spot when it's on the move (just as a tiger's stripes break up its outline). There's also a smaller-scale "micro pattern" that helps hunters blend into their environment when they're waiting to ambush a deer (similar to the function served by a leopard's spots).

But that's not all: The fabric's colors and patterns were fine-tuned to take advantage of the particular way deer and other hoofed animals (known as ungulates) process visual information. Jay Neitz, an animal vision scientist at the Medical College of Wisconsin, was called in to lend his expertise.

One big difference between deer and humans has to do with the placement of the eyes on the head. Our maximum field of view is about 180 degrees (with 140 degrees for binocular vision), while deer can take in nearly 280 degrees at a time - thanks to the fact that their eyes face in opposite directions rather than both facing forward.

That wider field makes it easier for the animals to get a low-resolution, all-around look at potential predators, but there's a trade-off: They can't process fine-scale detail as easily as we can. So clothing designed to mimic a deer's forest surroundings in detail doesn't work as well as you might think, Neitz told me.

"We could put all sorts of fine, beautifully detailed leaves in a camouflage pattern," he said. "The deer's vision system doesn't pick up all that fine detail. It just picks up the coarse view of a human form, and he'll say, 'Hey, there's a guy standing by that tree over there.'"

W.L. Gore & Associates

The Optifade pattern uses macro and micro patterns in muted colors.

The Optifade pattern is specifically designed to fool a deer's lower-resolution eye, Neitz said. And the color scheme does away with the usual forest green and brown. Instead, it emphasizes blue, black, white and gray - because those colors, plus yellow, are the only ones that a deer sees.

The eyes of a deer have the receptors for blue and yellow, but not for red, Neitz explained. As far as they're concerned, red is just another shade of gray.

From a scientific standpoint, perhaps the most interesting question is how scientists try to figure out what a deer sees. Neitz and his colleagues conduct experiments with animals who are trained to walk toward a particular type of pattern - for example, a card with black and white stripes on it vs. a gray card. The researchers modify the patterns by using different colors and widths of stripes, and eventually figure out what the animals can see and what they miss.

Deer aren't nearly as amenable to these sorts of tests as, say, lab rats. The experiments have to be conducted outdoors, under challenging conditions. "Those are really hard experiments to do," Neitz said. But once researchers figured out the way the deer vision system worked, they could create image-processing software that fuzz and fade a picture to duplicate a deer's vision.

Human subjects were then recruited to look at the resulting deer-cam video and pick out the camouflage patterns that maximized the wearer's invisibility. This video clip from W.L. Gore & Associates about the "Science of Nothing" provides plenty of examples.

For more examples, check out the deer's-eye view of a hunter in the trees vs. the human-eye view - or a picture of a hunter in an open field, as seen in human vision and deer vision.

The "Science of Nothing" video makes it look as if competing camo patterns would be much more easily seen by deer. But in this case, I suppose the true proof of the pudding is in the shooting - and I'm not aware of any scientific findings relating to Optifade's efficacy in the wild. During my youth in Iowa, I would occasionally go out hunting with my father - and I can tell you that deer-distracting camouflage wouldn't have made a bit of difference.

Does all this put you in the mood to learn more about different levels of visual perception? For an example that doesn't involve killing other living things, check out this Web page, which ties together visual spatial frequencies, Abraham Lincoln in the rough and Salvador Dali's wife in the nude.

Correction for 11:30 a.m. Dec. 11: I mistakenly typed "W.R. Gore & Associates" instead of W.L. Gore & Associates in an earlier version of this post. My deepest apologies to Mr. Gore ... and all his associates.

Correction for 8:20 p.m. Dec. 11: A sharp-eyed reader (who also happens to be an eye doctor) spotted my reference to the human field of view and upgraded it from 120 to 180 degrees. After a double-check, I've corrected the reference.

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